Management Induced Soil Change in Tennessee Valley (Alabama) Rhodic Paleudults.

The National Cooperative Soil Survey (NCSS) is emphasizing documentation of the variability of near-surface (0-50 cm) dynamic soil properties as a function of land use and/or management. Management affects soil organic carbon (SOC) pools, which are related to chemical properties, physical properties, and functions of soil. For this study, pools of SOC and management-dependent soil chemical and physical properties were measured on Decatur (Fine, kaolinitic, thermic Rhodic Paleudults) soils, a benchmark soil in the Tennessee Valley region of Alabama. These soil systems provide unique near-surface pedological environment for investigating soil organic matter and iron oxide interactions in highly weathered soils of the Southeastern United States. This region is intensively cropped and issues related to sustainable productivity, soil quality, and carbon sequestration are critical.  Management practices investigated include long-term (>10 years) pasture, as well as conservation and conventional cotton (Gossypium hirsutum) and grain row cropping systems. Significant differences (α=0.05) in active (potassium permanganate oxidizable) carbon, bulk density, and water stable aggregates were found at the soil surface (0-5 cm) among the difference management systems, but results were mixed at lower depths.  Evaluation of SOC pools, phosphorus retention, and anion exchange in these sesquioxide-rich soil systems will also be presented.